The present invention relates to a motion determining apparatus and a motion determining method for accurately determining the motion of a picture that is interlace-scanned.
When an interlace-scanned picture (hereinafter referred to as interlace picture) is converted into a non-interlace-scanned picture that is a progressively scanned picture (hereinafter this picture is referred to as progressive picture), coefficients such as tap coefficients of a filter used for the process are varied depending on whether or not the interlace picture moves so as to properly process the interlace picture. There are several types of converting processes such as a process for converting an interlace picture of one standard into an interlace picture of another standard; a process for converting a standard resolution interlace picture into a high resolution picture; and a process for controlling tap coefficients of a digital filter for detecting the motion of an interlace picture. In these converting processes, as a pre-process, it may be determined whether or not an interlace picture to be processed moves.
However, in a conventional motion determining apparatus, when only part of a considered field of an interlace picture is largely different from adjacent fields (for example, an interlace picture to be processed shows a jet plane that flies fast and disappears from the screen), although the part moves, it may be improperly determined that the part stops.
In this case, a process suitable for a picture that stops (for example, an inter-frame process for interpolating data of the current frame with data at the same position of the preceding frame) is performed for a picture that moves. The processed result is not a picture that smoothly moves. In addition, the process may fail in the middle.
On the other hand, although a picture that stops, when it is determined that the picture moves, a process suitable for a picture that moves (for example, an intra-field process) is performed. Thus, the picture that stops blurs.
Thus, the determined result of whether or not a picture moves largely affects a picture that is processed. Consequently, the motion determining process should be accurately performed (without error).
In addition to the process for an interlace picture, the motion determining process should be correctly performed for a progressive picture. A recursive noise reducing apparatus using the phenomenon of which a picture signal correlates on time axis but noise does not is known. With such a noise reducing apparatus, noise of a progressive picture can be reduced. The noise reducing apparatus determines whether or not a particular picture moves. When the motion of the picture is detected, the recursive process should be stopped. In addition, the contents of the frame memory should be rewritten. Thus, even in the noise reducing apparatus, unless the motion can be correctly determined, the above-described problem will take place.
Therefore, the present invention is made from the above-described point of view. An object of the present invention is to more accurately determine the motion of a picture than before.
The present invention is to solve the above-described problem. The invention of claim 1 is a motion determining apparatus for determining a motion of an object contained in an input picture signal, comprising a space variation detecting means for detecting a space variation of the input picture signal, a time variation detecting means for detecting a time variation of the input picture signal, a ratio detecting means for detecting the ratio of the space variation to the time variation, and a motion determining means for determining the motion of the object contained in the input picture signal according to the space variation, the time variation, and the ratio.
Preferably, the space variation detecting means detects a space variation of the input picture signal of the considered field corresponding to an input picture signal of a considered field and input picture signals of at least the fields that precede and follow the considered field. In the progressive system, a field is equivalent to a frame.
The invention of claim 11 is a motion determining method for determining the motion of an object contained in an input picture signal, comprising the steps of detecting a space variation of the input picture signal, detecting a time variation of the input picture signal, detecting the ratio of the space variation to the time variation, and determining the motion of the object contained in the input picture signal according to the space variation, the time variation, and the ratio.